Beam-compasses



(Model.)

L. K. DERBY.

Beafm Compasses.

ANo. 242,895. Patented .lune 14,1881.

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UNITED STATES PATENT OFFICE.A

' LOUIS K. DERBY, OF PHILADELPHIA, PENNSYLVANIA.

e EAM-M PAs'sEs.

SPECIFICATION forming part of Letters Patent No. 242,895, dated-June 14, 1881.

Application filed November 13, 1880. (Model.) y

To all whom it may concern:

Be it known that I, LoUIs K. DERBY, of Philadelphia, inthe county of Philadelphia and State of Pennsylvania, have invented a new and Improved Beam-Oom passes, of which the following is a specification.

The object of this invention is to provide a stronger, more accurate, and readily-adj ustable extension-Compasses for drawing purposes.

The invention consists of a T-shaped beam made in sections that are jointed and clamped together in a novel manner, and whose upper face is graduated in fractions of an inch, and whose Vernier, which is attached to the sliding leg, is also graduated; and it further consists of a pivoted eccentric-lever for adjusting and holding the sliding leg, all of which will be hereinafter set forth.

Figure 1 isa side elevation of the com passes. Fig. 2 is a plan of the same. Fig. 3 is a vertical elevation of the sliding leg in position. Fig. 4 is an enlarged side elevation ot a joint and clamp ofthe Compasses. Fig. 5 is an enlarged sectional plan View of ajoint and clamp of the compasseson line x ai, Fig. 4. Figs. 6 and 7 are front and side elevations of a pencil-socket to be secured on the end of the beam.

Similar letters of reference indicate corresponding parts.

In the drawings, A represents the beam, of T-shaped cross-section, having its upper face graduated, as shown at a., preferably to sixteenths of an inch, and provided on one end with a socket and set-screw, b c, for'holding pen or pencil, and having in the web of its other end a curved Inortise, d, to receive the hooked tenon f of a section, A', that may be used to lengthen said beam A. As many sections A' as may be desired may be used, all of them being counterparts of the beam A, and having in one end a mortise, d, and at the other a tenen, f. The sectionsAA' are held together not only by the engagement of a tenon,f, in a Inortise, d, but also by at clamping plates or couplings BB' and screw and nut B2 B3. One clamping-plate, B, is placed on one side of the joint formed by the union of the two sections A A', and the other plate, B', provided with a slot, g, is placed 011 the opposite side, against 5o the web of the device, and the screw B2 is then.

i passed through the plateB and a slot, h, formed in the tenon end of a beam-section, and through the slot g formed'in the plate B, and the nut B3 then screwed on it, as shown in Figs. 4 and 5, whereby the beam-sections are held firmly together. By forming the slots g h in the plate B' and beam-section A' the clamping-plates B B' may, on the loosening of the nut B, be moved back far enough to clear the joint and permit the disengagementof the beam-sections.

The sliding leg O is provided with the usual pin-point, lo, and, straddling' the beam A, is held in place by means of a U-shaped eccentriclever, C', that is pivoted between its sides, as shown at Z, with its legs extending upward and its eccentric convex crown bearing upon the upper face of the beam A. This lever C' is broadened at its point of contact with the beam A, as shown at on, for the purpose of giving it more bearing-surface, that it may hold theleg G more securely in place; and said lever C' is also provided with a spring, n, fastened to the extremity of one leg, as shown in Fig. 3, and having its other end pressing aga-inst the body of the sliding leg O, whereby said lever C' is held pressed on the beam A for keeping the leg C in place. On pressing back this spring n the pressure ot' the eccentric-lever C' upon the beam A is relaxed, and said beam A is then free to move. By removing the pressure on said spring n the lever G' will operate to hold the leg C in place, and said leg C can be clamped or held more tightly still by pressure in direction of the arrow, Fig. 3, upon the springless leg of the said lever C'.

The Vernier D is part of or attached to the sliding leg C, as shown in Figs. l and 2.

The pen E has one rib or side, o, made stiffer than the opposite rib or side, o', so that the pen-point will always accurately respond to the adjustment of the beam A and the spring of the pen be all on' one side. The pen E and the pencil-socket F have tlattened shanks p q, respectively, that are designed to be held in the socket b by the set-screw c at the free end of the beam A. A j

These Compasses possess advantages over others of like character in being strengthened and stiffened by being made T-shaped, in being graduated and at the same time having a graduated vernier, and in having an improved device for adj ust-in g the sliding leg, whereby IOO the adjustment can be made more quickly than 2. In beam-compasses,the combination,with

point 7c, straddling the T-beam A, and having f the U-shaped eccentriclever C pivoted in a socket thereof over the beam, as shown and 1o described.

the T-shaped beam A, of the T-shaped section A and couplings B B' B2 B3, substantially as herein shown and described, whereby the said Compasses are extended, as set forth.

'Louis Ko'ssUTH DERBY.

WVitn esses WALTER HARGRAVE, WM. D. TAYLOR. 

